Quantum Lab Session 2 Simulation Q5
✈️ Before we begin — what is "teleportation"?
Science fiction teleportation: you step into a machine in Mumbai, your body is scanned, destroyed, and rebuilt in Delhi. You feel fine. But quantum teleportation is completely different — and in some ways more mind-bending.

Quantum teleportation transfers the exact quantum state of a qubit from Alice to Bob — without the qubit itself physically travelling. Alice and Bob share an entangled pair. Alice measures her original qubit together with her half of the entangled pair. She gets 2 classical bits (0 or 1 each). She sends those 2 bits to Bob by phone, text, or radio. Bob applies a simple correction based on those 2 bits — and his qubit is now in exactly the state Alice's original qubit was in.

The original qubit at Alice's side is destroyed in the process (no cloning — we'll explore that in Q6). But the quantum state has been perfectly moved to Bob's side — no matter how far away he is.
🌀 Why this doesn't violate anything
The quantum state itself travels "instantly" via the pre-shared entanglement. But the 2 classical bits Bob needs to apply the correction travel at light speed. So the information always arrives at the speed of light or slower — no faster-than-light communication. The no-cloning theorem is respected — Alice's original is destroyed. Teleportation is real and has been demonstrated in labs over distances of 1,400 km (China, 2017).
✈️ Quantum Teleportation · Session 2 · Q5

Quantum Teleportation

Step through the world's most mind-bending protocol. Alice sends Bob a quantum state using entanglement and just 2 classical bits — no quantum channel needed.

🔧 Setup
📐 Alice Measures
📨 Send 2 Bits
🔧 Bob Corrects
🏆 Badge
🔗

Pre-shared entanglement

Alice and Bob share an entangled pair created beforehand. This is the "quantum channel."

📏

Alice measures

Alice measures her original qubit + her half of the pair. Gets 2 classical bits.

📡

Classical channel

Alice sends those 2 bits to Bob by any means — phone, email, radio. Light speed.

🔧

Bob corrects

Bob applies one of 4 possible gates based on the 2 bits. His qubit becomes the original.

✈️
Wizzy · Quantum Guide
Let's set the scene. Alice has a qubit in some unknown quantum state |ψ⟩ she wants to send Bob. She cannot copy it (no-cloning theorem). She has no quantum channel to Bob. But they pre-shared an entangled Bell pair earlier. That's all she needs!
🌀 The clever trick
Alice doesn't need a quantum channel — just 2 classical bits sent after her measurement. The entangled pair does all the quantum heavy-lifting. This is why teleportation is practical: quantum channels are hard; classical channels (phone, radio) are easy.

Step 1 — The Setup

Choose the state Alice wants to teleport to Bob:
Alice's side
Original qubit
?
Select state above
Alice's entangled qubit: A₂
⛓️
Bell
pair
⛓️
Bob's side
Waiting qubit
B
Entangled with Alice's A₂
Select the state Alice wants to teleport. Bob's qubit is already entangled with Alice's second qubit (A₂).
✈️
Wizzy · Quantum Guide
Alice measures her original qubit and her entangled qubit (A₂) together — a Bell measurement. This is a special joint measurement that gives her 2 classical bits. The exact bits she gets are random, but they encode everything Bob needs to reconstruct the state.
🌀 What the measurement does
Alice's Bell measurement collapses the 3-qubit system (original + A₂ + Bob's B). Whatever bits she gets, Bob's qubit instantly becomes "almost" the original state — off by a simple gate correction that depends on Alice's 2 bits.

Step 2 — Alice's Bell Measurement

Alice measures
?
Both qubits ready
→
affects
→
Bob's qubit
B
Affected by measurement
Alice's 2 classical bits
_ _
Press Measure to get the bits
Alice measures both her qubits jointly. She will get 2 random bits. These bits determine which correction Bob must apply.
✈️
Wizzy · Quantum Guide
Alice sends her 2 bits to Bob over a classical channel — a phone call, a text, a radio signal. This travels at the speed of light. That's the only limit on teleportation speed — not the quantum part, but the classical communication needed to complete it.
🌀 Why 2 bits are enough
There are only 4 possible measurement outcomes (00, 01, 10, 11). Each maps to exactly one correction gate for Bob. Two bits perfectly encodes which of these 4 corrections is needed. This is the "classical key" that unlocks the teleported state.

Step 3 — Classical Transmission

Bits being transmitted
_ _
Travelling at the speed of light via classical channel
Important: Bob cannot do anything useful with his qubit until he receives these 2 bits. The quantum state is "locked" until the classical key arrives. This is why teleportation can never be faster than light.
✈️
Wizzy · Quantum Guide
Bob receives the 2 bits and looks up the correction table. He applies the corresponding gate (I, X, Z, or ZX) to his qubit. After correction, his qubit is exactly the state Alice sent — even though no qubit ever physically moved between them! Click Apply Correction to see the magic!
🌀 Alice's original is now gone
Alice's original qubit was destroyed by her Bell measurement. The no-cloning theorem is respected — there is only one copy of the state. It now lives at Bob's side. The quantum state was teleported, not copied.

Step 4 — Bob's Correction

Correction lookup table:
Alice's bitsBob appliesEffect
00I (do nothing)Already correct
01X gate (flip)Flip 0↔1
10Z gate (phase)Flip phase
11ZX (both)Flip + phase
Original state (destroyed)
?
⟶
teleported
Bob's qubit (after correction)
?
Apply the correction to see Bob's qubit become the original state!
✈️
Wizzy · Quantum Guide
🎊 You've walked through the most sophisticated quantum protocol ever devised! In 2017, Chinese scientists teleported a photon's quantum state from Earth to a satellite 1,400 km away. This is the foundation of the future quantum internet.
🧠 What you actually learned today
  • Quantum teleportation transfers a quantum state without the qubit physically travelling — using a pre-shared entangled pair and 2 classical bits.
  • Alice's Bell measurement gives 2 random bits that encode which correction Bob needs to apply to his entangled qubit.
  • The classical bits must travel at light speed — so teleportation is never faster than light. No physics is violated.
  • Alice's original qubit is destroyed by the measurement — the no-cloning theorem is respected. There's only ever one copy.
  • The protocol works for any quantum state, even one Alice doesn't know — she doesn't need to know the state to teleport it.
✈️

Teleportation Master Badge!

You understood the protocol demonstrated over 1,400 km in 2017!

✈️ WhizzStep Quantum Lab
This certifies that
Student Name
has mastered Quantum Teleportation — Entanglement + Classical Bits
Teleportation
Bell Measurement
Quantum Protocol
📖 Quantum Vocabulary
Quantum teleportation NEW

Transferring a quantum state from one location to another using entanglement + 2 classical bits. The original state is destroyed.

Bell measurement NEW

A joint measurement of two qubits in the Bell basis. The result is 2 classical bits that encode the correction Bob needs.

Classical channel

Any ordinary communication method — phone, radio, internet. Travels at or below light speed. Needed to complete teleportation.

No-cloning theorem

You cannot copy an unknown quantum state. Teleportation respects this — the original is destroyed. Only one copy ever exists.

Pauli gates

X, Y, Z — the three basic single-qubit rotation gates. Bob uses X and Z (and their combination) as corrections in teleportation.

X flips 0↔1. Z flips the phase. I does nothing.

Key Concepts from Q5

Protocol

✈️ 3 Qubits, 2 Bits

Alice needs 3 qubits total (1 original + 2 from Bell pair) and sends 2 classical bits. Bob needs 1 qubit (his half of Bell pair) and receives 2 bits.

No FTL

🚦 Light Speed Limit

The quantum state doesn't travel — only the 2 classical bits do. Bob can't use his qubit until the bits arrive, preserving the speed of light limit.

Real World

🛰️ China 2017

Scientists teleported photon states from Earth to the Micius satellite 1,400 km above. It was the first space-to-ground quantum teleportation.

Future

🌐 Quantum Internet

Teleportation is the backbone of the quantum internet — allowing quantum states to be routed across long distances using quantum repeaters.